Vidalta
Active substance
ATC code
Species
Cats.
Indications
Treatment of hyperthyroidism and hyperthyroidism-associated clinical signs in cats.
Dose to be administered and administration route
For oral use only.
Administration with food enhances bioavailability. The timing of treatment and its relation to feeding should be kept consistent from day to day.
Do not break or crush Vidalta tablets as this will affect the sustained release property.
The aim of treatment is to maintain total thyroxine concentrations (TT4) in the lower end of the reference range.
The following dose recommendations during the adjustment and maintenance phases are suggested.
Dosing adjustment should primarily be based upon a clinical assessment of the individual cat. Monitoring of TT4, full haematology and liver and kidney parameters is recommended at each follow up visit (see sections 4.5 and 4.6).
Adjustment phase
The starting dose is a single daily oral administration of one tablet of 15 mg carbimazole per cat. Consideration could be given to a starting dose of one 10 mg tablet daily where the TT4 concentration is only mildly increased, e.g. between 50 nmol/L and 100 nmol/L.
With the recommended starting dose of one 15 mg tablet once daily, TT4 may decrease to within the euthyroid range (TT4<50 nmol/L) shortly after treatment initiation. A dose adjustment may be required as early as 10 days of treatment.
Dose adjustment should be also performed 3, 5 and 8 weeks after initiation of treatment, depending on both clinical and hormonal responses to treatment.
Maintenance phase
Follow-up visits every 3 to 6 months are recommended. The dose should be adjusted individually based on clinical signs and TT4. It is advisable to check TT4 10-14 days after dose adjustment.
The therapeutic dose ranges between 10 mg (one 10 mg tablet) and 25 mg (one 10 mg tablet and one 15 mg tablet) once daily.
Some cats require doses of less than 10 mg carbimazole daily. Every other day dosing with 10 mg or 15 mg of carbimazole may be sufficient to control the disease.
Dose increases should not be made in increments of greater than 5 mg.
Doses above 20 mg have only been trialled in a small number of cats and should be used with caution.
Adverse reactions
Treatment of hyperthyroidism may result in a reduction of renal perfusion. Azotaemia has been reported in rare cases; depending on the severity, temporary or permanent discontinuation of treatment may be required. Polydipsia and polyuria have also been reported in rare (polydipsia) or very rare cases (polyuria).
Weight loss, vomiting, lethargy, tachycardia, reduced appetite, diarrhoea and dehydration have been observed in rare cases.
Increased liver enzymes have been reported in rare cases. Severe cases may require temporary or permanent discontinuation of treatment. However, these elevations are usually reversible when treatment is discontinued, although symptomatic therapy (nutritional and fluid support) may be required.
Anaemia, increase or decrease in white blood cell count, neutrophilia, thrombocytopaenia, eosinophilia and/or lymphopaenia have been reported in rare cases, in particular during the first 4-6 weeks of treatment. Discontinuation of treatment may be required in case of persistent and marked disorder. In most cases, the abnormality will resolve spontaneously within 1 month after the treatment has been discontinued.
Dermatological signs (pruritus, dermatitis, erythema, alopecia) have been reported in rare cases. These clinical signs are usually mild, adequately controlled by symptomatic therapy and do not require discontinuation of treatment. However, if more severe clinical signs occur that do not respond to symptomatic therapy, the dose should be reduced or treatment stopped following a benefit-risk assessment by the responsible veterinarian.
Signs of gastrointestinal bleeding such as bloody vomit, oral haemorrhage or dark faeces have been reported in rare cases.
Ataxia, pyrexia, dyspnoea, disorientation, aggressiveness, and positive antinuclear antibody (ANA) have also been reported in very rare cases.
In cases of serious adverse reactions, mortality, possibly due to the product, might occur if treatment is not discontinued. In many cases adverse reactions are reversible on cessation of treatment.
The frequency of adverse reactions is defined using the following convention:
- very common (more than 1 in 10 animals treated displaying adverse reactions)
- common (more than 1 but less than 10 animals in 100 animals treated)
- uncommon (more than 1 but less than 10 animals in 1,000 animals treated)
- rare (more than 1 but less than 10 animals in 10,000 animals treated)
- very rare (less than 1 animal in 10,000 animals treated, including isolated reports).
